Conventionally, air conditioning control of controlled spaces wherein a plurality of variable air volume (VAV) units is disposed is performed through calculating the air volume to be blown by each individual VAV unit based on a load. Moreover, a supply rating (for example, 4000 CMH) and a minimum outside air volume (for example, 1000 CMH) are established in advance for the air conditioner, and a maximum air volume (for example, 1000 CMH) and a minimum air volume (for example, 200 CMH) are established for the individual VAV unit. There is the constraint of the minimum required volume on the total of the air volumes blown into the controlled space due to the need for air exchange in order to maintain the environment of the controlled area. The minimum air volume for each VAV unit in the controlled area is set to a quantitative value that is larger than zero, in order to ensure the minimum value for the total air volume.
FIG. 5 is a diagram illustrating an example of a minimum air volume setting in a conventional air conditioning system. The air conditioning system illustrated in FIG. 5 has an air conditioner 1; a cold water valve 2 for controlling the volume of cold water to the air conditioner 1; a hot water valve 3 for controlling the volume of hot water to the air conditioner 1; a supply duct 7 for supplying supply air from the air conditioner 1 to a controlled space 9; VAV units 8-1 through 8-4 for controlling, for individual controlled areas Z1 through Z4, the volumes of supply air supplied into the controlled space 9; VAV control units 11-1 through 11-4, which are control devices for controlling the VAV units 8-1 through 8-4; temperature sensors 12-1 through 12-4, for measuring, for each controlled area Z1 through the Z4, the room temperature of the controlled space 9; an outside air damper 13 for adjusting the volume of outside air that is drawn into the air conditioner 1, and a temperature sensor 14 for measuring the temperature of the supply air. The air conditioner 1 is structured from a cooling coil 4, a heating coil 5, and a supply air fan 6. 10-1 through 10-4 in FIG. 5 are blower openings for the supply air.
In the example in FIG. 5, the air volume of the VAV unit 8-1 for the controlled area Z1 is 900 CMH, the air volume for the VAV unit 8-2 for the controlled area Z2 is 700 CMH, and the air volumes for the VAV units 8-3 and 8-4 for the controlled areas Z3 and the Z4 are each 200 CMH. That is, because the air conditioning load is low for the controlled areas Z3 and Z4, the air volumes for the VAV units 8-3 and 8-4 are set to be small air volumes. In this way, when the air volumes of the VAV units 8-3 and 8-4 are set to the minimum air volumes, it is not possible to reduce the air volumes further, and thus there are constraints on the controllable temperature range, leading to the possibility that the room temperature will become too low in the case of a cooling operation, or the room temperature may become too high in the case of a heating operation.
Given this, technologies have been proposed for improving the limitations on control through constraining, through the minimum air volume setting values, the air volumes for the individual controlled areas while maintaining the total air volumes to values that are no less than a total air volume minimum value (See Japanese Unexamined Patent Application Publication 2010-79378 (“JP '378”) and Japanese Unexamined Patent Application Publication 2010-79381 (“JP '381”)). The technologies disclosed in JP '378 and JP '381 determine the air volume for each individual VAV unit so that the total of the air volumes of all of the individual controlled areas will be no less than a total air volume lower limit value when the total of the required air volumes (operating quantities) for the individual controlled areas is less than the total air volume lower limit value.
FIG. 6 is a diagram illustrating the minimum air volume settings based on the technologies disclosed in JP '378 and JP '381. In the example in FIG. 6, the air volume of the VAV unit 8-1 for the controlled area Z1 is 900 CMH, the air volume for the VAV unit 8-2 for the controlled area Z2 is 700 CMH, the air volume for the VAV unit 8-3 for the controlled area Z3 is 50 CMH, and the air volume for the VAV unit 8-4 for the controlled area Z4 is 100 CMH. Consequently, the total air volume is 900 CMH+700 CMH+50 CMH+100 CMH=1750 CMH.
In this way, in the example in FIG. 6, the total air volume will be a value that is no less than the 100 CMH of the total air volume lower limit value, and the minimum air volume setting values of the VAV units 8-3 and 8-4 for the controlled areas Z3 and Z4 are reduced in accordance with the loads of the controlled areas Z3 and Z4, making it possible to relax the minimum air volume setting value control, and to resolve the problem of the room temperature becoming too low during a cooling operation or the room temperature becoming too high during a heating operation. Moreover, in the example in FIG. 6, it is possible to reduce the energy consumption when compared to the example in FIG. 5, by reducing the total air volume.
In the conventional technology, when the total air volume falls below the total air volume lower limit value because a VAV unit is stopped or because the air conditioning load has decreased, there is the potential for problems such as the following to arise due to handling by increasing the minimum air volume setting values. FIG. 7 and FIG. 8 are diagrams for explaining the conventional problem areas. In the example in FIG. 7, the air volume of the VAV unit 8-1 for the controlled area Z1 is 750 CMH, the air volume for the VAV unit 8-2 for the controlled area Z2 is 100 CMH, and the air volumes for the VAV units 8-3 and 8-4 for the controlled areas Z3 and the Z4 are each 0 CMH. Among these, the air volume for the VAV unit 8-3 for the controlled area Z3 goes to 0 CMH because there is no air conditioning load, and the air volume for the VAV unit 8-4 for the controlled area Z4 goes to 0 CMH because the control has been terminated. The total air volume is 750 CMH+100 CMH+0 CMH+0 CMH=850 CMH, falling below the total air volume lower limit value of 1000 CMH.
In the conventional technology, when a situation as illustrated in FIG. 7 occurs, the handling is to increase the lower limit air volume setting values, as illustrated in FIG. 8, in order to maintain the total air volume as a whole. In the example in FIG. 8, the minimum air volume setting values for the VAV units 8-2 and 8-3 for the controlled areas Z2 and Z3 are set to 1125 CMH. As a result, the total air volume goes to 750 CMH+125 CMH+125 CMH+0 CMH=1000 CMH. In this way, the conventional technology is able to maintain the total air volume at a value that is no less than the total air volume minimum value.
However, notwithstanding the fact that the load for the controlled area Z2 is small, still the air volume is increased from 100 CMH to 125 CMH, and notwithstanding the fact that there is no load for the controlled area Z3, the air volume is increased from 0 CMH to 125 CMH, and thus an air volume that is greater than that which is necessary is provided, and there is the possibility that the room temperature will become too low during cooling operations and the room temperature will become too high during heating operations. Note that a similar problem occurs also when there is insufficient outside air.
What is needed is to solve the problem areas set forth above, and the object thereof is to provide an air conditioning controlling device and method able to improve the ability to control the temperature within the room while, at the same time, increasing the total air volume to a value that is no less than the total air volume lower limit value when the air volume is insufficient.